The present invention relates to a method of determining a core-less machining shape using a system for creating NC data for wire-cut electric discharge machining such as an automatic programming device, a CAD/CAM system, a numerical control device or a wire-cut electric discharge machine, and an apparatus for carrying out the method and a storage medium storing a program for determining the core-less machining shape.
As ablation machining performed by the wire-cut electric discharge machining, there are known contour machining in which cutting is performed along a contour of a machining shape and then a core is removed manually, and core-less machining in which machining is started from a prepared hole inside a machining shape and all the portion inside the contour of the machining shape is removed by the electric discharge machining. The former is suitable for machining of a relatively large shape, while the latter is suitable for machining of a relatively small shape and contributes to reduction of overall time of the machining since the latter machining does not involve process of manually removing a core.
For reducing overall time required for the wire-cut machining, it is important to selectively apply contour machining and core-less machining in dependence on a size of a machining shape.
It is generally adopted to design a shape of a product to be machined using an automatic programming device and a CAD/CAM system. In such system, attributes of objects (i.e., machining shapes) are managed for each object, separately. Attributes are designated to objects in a manner that objects are selected one by one and attributes are designated to each object, or in a manner that groups consisting of a plurality of objects are formed in advance and attributes are designated to all the objects belonging in each group, or in a manner that attributes are designated to all the objects included in each specific layer. In any case, judgment of which attribute should be designated to a specific object is totally left to an operator.
Thus, an operator needs to decide on his or her own whether an attribute of the contour machining or an attribute of the core-less machining should be designated to a machining shape. In particular, there is a problem that it is difficult to judge a size of each machining shape, after the whole process of designing has been completed and many objects have been created. Further, oversight may happen in selecting objects one by one or forming groups of objects, so that an appropriate attribute may fail to be designated to a machining shape. It is technically possible to provide a layer for the contour machining and a layer for the core-less machining in advance, and to manage contour machining shapes and core-less machining shapes based on the layers. However, if it becomes later necessary to change a criterion for judging the size and therefore to change the designated attributes, the same problems will arise such as the difficulty of judging the size of the machining shape and the oversight.
CAD software having an information pallet for indicating attributes of objects and capable of providing attribute information such as a position in X-Y coordinate system, maximum dimensions in horizontal and vertical directions, a diameter or a radius, etc. of a selected object in the form of numerical data so that the information can be checked easily is available on the market. Such CAD software is useful in judging whether an attribute of the contour machining or an attribute of the core-less machining should be designated. However, it requires selecting objects one by one, checking information about each object and then designating an attribute. Thus, it requires cumbersome operations in the system, and problems such as oversight as mentioned above remain unsolved.
An object of the present invention is to provide a method of and an apparatus for determining a core-less machining shape, in which an attribute of core-less machining or an attribute of contour machining can be automatically designated to a machining shape, and a computer readable storage medium storing a program for determining a core-less machining shape.
A core-less machining shape determining method of the present invention comprises the steps of: judging a size of a machining shape based on data of the shape created in advance, and automatically determining appropriate attributes to one group of the machining shapes or both group of the machining shapes, to designate a core-less machining to a machining shape having a size equal to or smaller than a set value, and designate a contour machining to a machining shape having a size larger than the set value. The present invention also provides an apparatus for creating NC data for wire-cut electric discharge machining, which performs the above core-less machining shape method. Further, a program for determining whether or not the core-less machining is applied to a machining shape and automatically designating an appropriate attribute to the machining shape is stored in a storage medium, and such program is executed by a computer in a device for creating NC data for the wire-cut electric discharge machining.
More specifically, only an attribute of the core-less machining is designated to a machining shape which has a size equal to or smaller than a set value, or only an attribute of the contour machining is designated to a machining shape which has a size larger than the set value. Alternatively, an attribute of core-less machining is designated to a machining shape having a size equal to or smaller than the set value, and also an attribute of contour machining is designated to a machining shape having a size larger than the set value.
Further, one or more ways of judgment are selected from a plurality of ways of judgment for determining a size of a machining shape, a logical product or a logical sum is selected as a logical operation to be performed on the result of the selected ways of judgment, and the selected logical operation is performed on the result of the selected ways of judgment to judge the size of a machining shape and designate an attribute of the core-less machining or an attribute of the contour machining to the shape.